Should They Ban Motorcycles from Cycling Races?

The former Belgian top cyclist Johan Museeuw once stated: “Crashing is part of cycling as crying is part of love.” Indeed, probably every elite cyclist has experienced in-race crashes that put him or her in the hospital. But recently, things seem to have become much worse. In the past two years, many prestigious elite races have been stained by serious crashes between riders and in-race motorcycles. The tragic culmination so far of these crashes was reached on 27 March 2016, when Belgian rider Antoine Demoitié got hit by a motorcycle in the race Gent-Wevelgem and died later in hospital due to his injuries. Later, on 28 May 2016, 19 cyclists were involved in a major crash with two motorcycles, which put Belgian rider Stig Broeckx in hospital in a coma.

The many crashes made us decide to investigate the aerodynamic effects of motorcycles riding in the vicinity of cyclists. Cycling races contain a multitude of motorcycles, which can be neutral support motor cycles, race officers, doctor and police or press motorcycles, where the latter can be camera, sound or photographer’s motorcycles. The press motorcycles are allowed to maneuver in the proximity of the cyclists when their passengers are filming or recording what is only forbidden in the last 500 m of the race (UCI 2016). For individual time trials, following vehicles (which can be cars or motorcycles) are requested to follow at least 10 m behind the riders (UCI 2016). However, this rule is not strictly enforced and especially press motorcycles often ride much closer to the cyclists.

Individual time trials with riders followed by motorcycles and/or cars.

Individual time trials with riders followed by motorcycles and/or cars.

To quantify the influence of these following vehicles, we performed a series of CFD simulations for different configurations of a motorcycle and a cyclist. We focused on a cyclist in time trial position at typical time trial speed of 54 km/h, because the aerodynamic benefits — if relevant — will be more decisive in time trials. The CFD simulations were done at Eindhoven University of Technology in the Netherlands with the ANSYS code. They were successfully validated with wind-tunnel measurements at the University of Liege in Belgium.

Pressure coefficient contours in vertical center plane through middle of cyclist and motorcycle. Distance in between is 1 m. Cycling speed is 54 km/h.

Pressure coefficient contours in vertical center plane through middle of cyclist and motorcycle. Distance in between is 1 m. Cycling speed is 54 km/h.

The aerodynamic benefit is of course a function of the distance between cyclist and motorcycle, and of the number of motorcycles following the cyclist. The drag reduction goes up to 8.7% for a single trailing motorcycle and to 13.9% for three trailing motorcycles at a short distance behind the cyclist. This could translate to a time reduction of more than 100 s on a 50 km time trial.

To answer the question stated in the title: no, it is not needed to ban motorcycles from cycling races, but it seems urgently needed to enforce a minimum distance between the motorcycles and the riders, not only to avoid unwanted aerodynamic benefits, but also to avoid further accidents. We call upon the International Cycling Union to take action before the start of the Tour de France by issuing a set of safety regulations for motorcycles.

Pressure coefficient contours in vertical center plane for cyclist followed by one, two or three motorcycles for separation distances from d = 0.25 m up to 7.5 m. Cycling speed is 15 m/s.

Pressure coefficient contours in vertical center plane for cyclist followed by one, two or three motorcycles for separation distances from d = 0.25 m up to 7.5 m. Cycling speed is 15 m/s.

ansys webinars this weekPlease join me on June 29 for the Cycling webinar from the Sports Webinar Series during which I will review these results in much more details. I will also reveal some new and yet unpublished findings.

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About Bert Blocken

Bert Blocken is full professor at the Department of the Built Environment at Eindhoven University of Technology in the Netherlands and part-time full professor at the Department of Civil Engineering at Leuven University in Belgium. His main areas of expertise are Urban Physics and Environmental Wind Engineering. He has published 113 papers on these topics in international journals with peer review. He has received several national and international awards, including the 2013 Junior Award from the International Association of Wind Engineering. He is currently supervising a team of 4 postdoctoral fellows, 24 PhD students, 1 PDEng student and 11 MSc students. Website: www.urbanphysics.net